They are 18 to 20 feet high and 50 feet long. Colouration is green to greenish brown with paler green underparts and lime-green spots on the wings of older wyverns. In flight their call is similar to a crow, while they roar when attacking. They eat any large African mammals. The nomadic wyvern sometimes makes nests on crags. The wyvern egg is very large with a thick bumpy shell which changes colour to match its surroundings. The chicks are brown and lose their spines as they get older.